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Steam Regeneration; 2. Reversed Brayton Heat Cycle Regeneration; and 3. Nitrogen based Carbon Bed Regeneration. However, the location of the emissions, as well as the emission rates from the production and curing of flexible slabstock, are imposing prob- lems on vapor collection and concentration.

Intellectual owner is Unifoam, Switzerland, who has patented this process world- wide. Briefly described under section 3. Foam is poured by the Maxfoam Process in a slab-sized mold and closed immediately afterward. The mold is connected to a closed loop exhaust system, including both a sacrificial prefilter and a carbon adsorption unit. This system traps all emissions and allows subsequent recovery of the blowing agent.

Handbook of Foaming and Blowing Agents | Chemtec Publishing

Because the production of a mold of foam is essentially iden- tical to a run of slabstock foam, and the yield of a run is directly related to the run length, the metering technology is of extreme importance, and should approach those of the molding technol- ogy in precision and directness. E-Max is an intermittent pro- duction process. Periflex is currently constructing a full size unit that will be operational and open for demonstration in the second quarter of Hypercure is an add-on technology to the Vertifoam process. Developed by Hyman, Great Britain, the technology was first described in during a conference of the Society of Plastics Industry.

The Vertifoam technology produces a foam block with a thin, porous skin, allowing CFCs to be emitted at a faster rate than traditional or Maxfoam processes. This feature was used as the base for the so called "rapid cure" system: under continuous controlled conditions, foam blocks are quickly cooled to ambient or safe handling temperature. This also provides an opportu- nity to terminate unreacted isocyanates under controlled con- ditions, as well as concentrate auxiliary blowing agents for efficient recovery.

Add-on recycling for flexible foam was first described in Now, several pilot plants have shown its feasibility for Tradi- tional and Maxfoam equipment, and machine suppliers all over the world are offering equipment that is suitable for connection to existing foaming units. These systems are very effective in the recovery of blowing agents from the process exhaust, but at best are unproven in their efficiency on emissions from the curing area.

Encapturement of the air, although theoretically possible, has shown to be technically difficult, cost prohibitive, and less efficient. However, the ongoing development in this area, combined with future broader regulations on air emissions, may turn the tide in favor of this type of conservation. A technology using the reversed "Braysorb Cycle" may reduce the need for extensive and expensive carbon beds Nucon, Co- lumbus, Ohio.

Other adsorbents DOW , may prove to be more effective on dilute vapor concentration. In an era where emissions are subject to scrutiny, and where conservation efforts are increasingly significant, recovery and recycling deserve continuing attention. General description Methylene chloride is a widely used chemical solvent with a diverse number of applications including use as an auxiliary blowing agent for flexible slabstock polyurethane foam. Substi- tuting methylene chloride for CFC is an immediate technical and commercial option.

Handbook of Foaming and Blowing Agents (Hardback)

Methylene chloride has been used successfully for many years in the production of flexible slabstock foam. In the U. The cost of methylene chloride is signifi- cantly less than CFC However, its classification as a "probable human carcinogen" by the U. In many instances, this solvent may provide the most expeditious manner for eliminating the use of CFC and come closest to being the one alternative to CFC However, it is recognized that specific reasons exist in some geographic areas to mitigate against the use of methylene chloride.

Therefore, manufacturers of flexible polyurethane foam must find the best alternative for their specific needs and requirements economically, geographically, and legally.

Principles Like CFC, methylene chloride functions as an auxiliary blowing agent. It vaporizes from the heat of reaction in the slabstock foam. This vaporization removes heat from the foam. The agent increases expansion of the foaming mass to lower the density and soften the foam. Remaining within the applicable regulations for methylene chloride exposure in the workplace is a primary consideration, as it is for handling all chemicals. However, foam plants are ventilated to manage TDI exposure; experience has shown that further modifications for handling methylene chloride vapors are minor.

Ranges and limits Methylene chloride can be used worldwide to manufacture all grades of foam, including supersofts, high resilience HR , and combustion modified high resilience CMHR. Methylene chlo- ride is routinely used in all types of flexible slabstock foam production equipment. The health effects of methylene chloride have been studied extensively. Laboratory results have shown an increased inci- dence of lung and liver cancer in mice, but not in rats or hamsters. Two epidemiology studies of workers exposed to the chemical over an extended time have shown no increased overall risk of cancer.

EPA has classified methylene chloride as cat- egory B2 or a "probable human carcinogen. Foam manufacturers considering a switch to methylene chloride must first consider the regulatory impact on a specific plant location. Changes Required Because the allowable exposure levels for methylene chloride are lower than CFC, some increase in ventilation may be required in a plant making a conversion.

This has not been found to be a problem on most foam lines where large volumes of air are being removed already to control TDI exposure. In the bun storage room, methylene chloride concentrations are some- times higher near floor level. Switching from CFC to methylene chloride requires an increase in tin catalyst to prevent splits. This tin increase is usually associated with either a lowering of the amine catalyst or a switching of amines in instances where processing param- eters are critical.

Except for these minor differences and some adjustments, methylene chloride can be used as a substitute for CFC LCP Chemicals, Inc. Occidental Chemical Corp. Methyl chloroform General description 4.

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It was recently introduced as an auxiliary blowing agent for flexible slabstock polyurethane foam. The diversity of state and local regulations pertaining to the use of CFC and other auxiliary blowing agents lead to a search for short term alternatives that could be used with relative simplicity.

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As flexible slabstock producers move away from CFC and in areas where methyl- ene chloride use is not possible, methyl chloroform has provided a viable solution. Its ozone depletion potential is 0. This technology is, therefore, a short term bridge from CFC to other solutions. Like CFC, methyl chloroform vaporizes from the heat of reaction in the slabstock foam. The vaporized blowing agent increases the expansion of the foaming mass and thereby lowers the density and softens the foam. Foam plants are ventilated to manage TDI exposure, and experience has shown that further plant modifications for handling methyl chloroform vapors are negligible.

Certainly, no increase in ventilation is expected if methylene chloride was used previously. Ranges and limits Methyl chloroform is used commercially in the U.

Handbook of Foaming and Blowing Agents

S to produce a wide variety of foam grades. In addition, because of the higher boiling point of methyl chloroform, processing improves in warmer climates or by using warmer components. Due to the high volumes used globally and its potential to contribute to ozone depletion, methyl chloroform has been added to the list of ozone depleting substances under the Montreal Protocol, where reductions start in with a phaseout by Changes required Since the allowable exposure levels for methyl chloroform are lower than CFC, some increase in ventilation may be re- quired in a plant making a conversion.

This has not been a problem on most foam lines where large volumes of air are being removed already to control TDI exposure. In the bun storage room, methyl chloroform concentrations are sometimes higher near floor level and require added ventilation. When switching from CFC to methyl chloroform, an in- crease in tin catalyst is required.

Except for these minor differences and some adjustments, methyl chloroform can be used as a substitute for CFC HCFCs are largely broken down in the lower atmosphere, or troposphere, so that only a fraction of HCFCs emitted will migrate to the stratosphere. Their ozone depletion potentials are 0. Because of the chlorine contained in these compounds, addi- tional limits may be imposed on the HCFCs by subsequent updates of the Montreal Protocol.

Changes required Based on currently available information, the changes in foam processing will be similar to those required for conversion from CFC to methylene chloride or methyl chloroform.